Various measuring and drawing tasks are performed by people from all walks of life, e.g. draftsmen, designers, engineers, artists, and children learning geometry. A wide variety of instruments exists to assist such people in performing the various drawing and measurement tasks. Examples of these instruments include compasses, straight edges, rulers, protractors, templates, and french curves. Thus, performance of numerous measuring and drawing tasks has required both proficiency at using a variety of instruments and the physical collection of such instruments.
Sometimes the functions of different instruments have been combined into a single instrument. For example, some devices combine a straight edge, ruler, and template. Other devices combine compasses, straight edges, and rulers by using a disk rotatably mounted in a rigid sheet. The rigid sheet includes a straight edge having markings for drawing straight lines or measuring between points. The sheet and disk further include holes for receiving a writing instrument to form arcs and circles as with a compass. For instance, a user would hold the rotatable disk over a pad of paper, insert a writing instrument into one of the holes in the rigid sheet, and rotate the sheet and writing instrument about the disk to form a constant radius arc. One problem with such devices is the relatively limited number of functions that can be performed. For example, precise angles cannot be measured and drawn. Other disadvantages include the complexity of some devices, particularly if such devices are to be used as educational tools for children.
Still other devices, such as that disclosed in Kirkegaard, U.S. Pat. No. 3,474,538, have a single plate configured to perform the functions of straight edge, ruler, template, protractor, and compass. Although such a device can be used for a variety of functions, it cannot be used as easily or as accurately as often desired. Again, this is particularly true if the device is to be used by children learning to draw and measure various geometrical configurations. Also, the Kirkegaard device does not include a rotatable dial or disk to help a user draw both arcs and angles.
Another common problem with existing designs is the crowding of components and the difficulty in perceiving the meaning of the various scales and marks. A person experienced in the use of rulers, protractors, and compasses would be able to understand and use at least some of the existing devices, but it would be more difficult for others, such as children learning geometry. Another problem is the lack of visual indicators to teach the importance of various functions, numbers, and scales.
It would be advantageous to have a device which combines various measuring and drawing functions while maintaining an understandable and usable overall design.